Adapter circuit for use with auto exposure camera

ABSTRACT

An adapter circuit is coupled to a light integrating automatic exposure control circuit of a camera to effect Flashing and Quenching operations of an associated Electronic Flash unit over a two wire connection therebetween. The adapter circuit precludes the transmission of a quench control signal from the camera to the Flash unit until a return signal, representative of a firing of the Flash unit, is received from the Flash Unit.

United States Patent 1 1 Wilwerding 1 Dec. 4, 1973 [54] ADAPTER CIRCUIT FOR USE WITH AUTo 3,646,865 3 1972 Riber 95 10 c5 EXPOSURE CAMERA 3,601,022 8/1972 95/10 C 1 3,688,659 9/1972 Takishima et a1. 95/10 CT [75] Inventor: Dennis J. Wilwerding, Littleton,

C010 Primary ExaminerSamue l S. Matthews [73] Assignee: Honeywell Inc., Minneapolis, Minn. Assistant Examiner-Russell Adams,

AttorneyArthur H. Swanson et a1. 22 F1led: Aug. 11, 1972 [21] App]. No.: 279,989 [57] ABSTRACT An adapter circuit is coupled to a light integrating au- [52] US. Cl. 95/10 CE, 95/1 1.5 tomatic exposure control circuit of a camera to effect 51 Int. Cl c031, 15/05, G03b 9/70, G03b 7/16 Flashing and Quenching Operations of an associated 5 Field f Search 95 0 C, 10 CE, 10 CT, Electronic Flash unit over a two wire connection 95 /1 L5 therebetween. The adapter circuit precludes the transmission of a quench control signal from the camera to 5 R f r Cited the Flash unit until a return signaLrepresentative of a UNITED STATES PATENTS firing of the Flash unit, is received from the Flash U L 3,614,918 10/1971 Hennig et a1 95/10 C m 3,638,543 2/1972 Kondo 95/10 CE 7 Claims, 6 Drawing Figures f 26 F I A '23 8 s H u T T E R I F i 24 ADAPTER )27A 1 CONTROL CIRCUIT 'I i c 1 R c: u T g i J 1 -1 5/ I F LA 8 H I U N I T PATENTEUUEII 41915 3.776.12

I sum 30F 3 YFIG.4V

1 ADAPTER CIRCUIT FOR USE WITH AUTO EXPOSURE CAMERA Subject matter disclosed but not claimed herein is disclosed and claimed in the following copending applications: Ser. No. 108,876 by Francis T. 'Ogawa, filed Jan. 22, 1971; Ser. No. 108,878 by Francis T. Ogawa, filed Jan. 22, 1971; and Ser. No. 279,988 by Francis T. Ogawa filed on even date herewith.

The present invention relates generally to automatic exposure control circuitry and more particularly to an adapter circuit for transmitting flash control and quench control signals from an automatic exposure control camera means to an electronic flash unit, via a two wire connection.

Automatic electronic shutter control or exposure control circuits are well known in .the art. Such circuits respond to a selective actuation of a switching means,

usually a shutter release switch of a camera, to open and/or hold an exposure controlling device or shutter whereby to allow light from a scene being photographed to expose a light sensitive film within the camera. A light integrating means then measures thelight being received from the scene being photographed, and generates a signal effective to close the exposure controlling device or shutter when a predetermined amount of integral light has been received. When the exposure controlling device is mechanical in nature, an appreciable time delay will elapse before the mechani-. cal exposure terminating device completely terminates the exposure of the light sensitive film to the light from the scene being photographed in response to the exposure terminating signal generated by the lightintegrating means. When ambient light is insufficient to properly expose the light sensitive film, and auxiliary light is provided in the form of an electronic flash unit, the

response time of the mechanical exposure controlling,

device is too slow to be effective. Hence, means must be provided to quench the light source. The so called computer flash photographic systems provide that requisite quenching means. However, where the lightsensor is in the camera, most computer flash systems have heretofore required a minimum of three wires connecting the camera and the flash unit. Since the wire cables and connections are of standard manufacture, a twowire system for coupling an electronically controlled shutter camera with a quenchable electronic flash unit is highly desirable. One such system is shown in FIG. 11 of US. Pat. No. 3,638,543 which issued to lsao Kondo on Feb. 1, 1972. While the Kondo circuit is generally of the two-wire type, the quenching circuit portion thereof is susceptable to being falsely actuated by spurious noise signals. That susceptability is a definite shortcoming particularly in systems which provide an indication to a photographer when a quenching operation has occurred. The photographer assumes by such an indication that proper exposure has been accomplished. If the quenching operation is falsely initiated for example by noise signals, the photographer is misled into believing that a particular scene hasbeen properly exposed when in fact it hasnt. The photographer will not discover his error until the film is developed, at which time it is at least inconvenient, if not impossible, to reconstruct that particular scene. Therefore, there is a need for an adapter or coupling circuit for coupling an electronically controlled shutter type camera to an electronic flash unit using only a two wire connectionv therebetween and which is substantially insensitive to noise signals otherwise operative to effect a false quenching operation of the flash system.

It is accordingly an object of the present invention to provide an adapter circuit which obviates the disadvantages of prior art apparatus.

It is another object of the present invention to provide an adapter circuit which couples an automatic electronic shutter camera with an electronic flash unit using a two Wire only connection therebetween.

It is a further object of the present invention to provide an adapter circuit as set forth which significantly reduces the possibility of a noise signal effecting a false quenching of the Flash unit.

In accomplishing these and other objects, there has been provided, in accordance with the present invention, an adapter circuit which is coupled to an automatic exposure control circuit of a camera and connected to an associated electronic flash unit by a twowire connection means. A switching means associated with the camera is selectively actuated to open an exposure control device or shutter, thereby exposing a light sensitive film in the camera, and to generate a flash control signal which is transmitted over the two wire connection means to fire the flash unit. A return signal representative of the firing of the flash unit is transmitted over the two-wire connection means back to the adapter circuit. A light sensing circuit within the automatic exposure control circuit of the camera, generates .a terminate signal, effective to close the exposure control device when a predetermined amount of light has been received from the scene being photographed. The adapter circuit, after receiving the Return signal, responds to the terminate signal to effect the initiating of the quenching operation of the flash device.

A better understanding of the present invention may be had from the following detailed description, when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a typical automatic exposure control circuit of a camera;

FIG. 2 is a schematic diagram of a computer flash system using the adapter circuit of the present invention.

FIG. 3 is a schematic diagram of an electronic Flash unit which may be used with the present invention;

FIG. 4 is a schematic diagram of one embodiment of the present invention;

FIG. 5 is a schematic diagram of another embodiment of the present invention; and

FIG. 6 is a schematic diagram of a further embodiment of the present invention I Referring in detail to FIG. 1, there is shown a typical shutter control circuit 1 for an electronically controlled shutter camera. A power supply 2 has a positive terminal connected through a switching member S1 to a power lead 3. A negative terminal of the power supply 2 is connected to a reference lead 4. Aswitching member S2 connects the power lead 3 to one terminal of a light sensor 5, such as the silicon type, the other terminal of which is connected through a resistor 6 to the base terminal of a transistor 7. The base terminal of the transistor 7 is also connected through a resistor 8 to one terminal of a capacitor 9, the other terminal of which is connected to the reference lead 4. The emitter terminal of the transistor is connected through a reistor 10 to the reference lead 4, while its collector terminal is connected to the base terminal of another transistor 11. The emitter terminal of the transistor 7 is also connected through a resistor 12 to one terminal of a diac 13, the other terminal of which is connected to the power lead 3. The emitter terminal of the transistor 11 is connected to the power lead 3; its collector terminal is connected through a resistor 14 to the reference lead 4. The collector terminal of the transistor 11 is also connected to a point 16 and then through a resistor to the base terminal of a transistor 17. The emitter terminal of the transistor 17 is connected to a point 18 on the power lead 3 and its collector terminal is connected to a point 19. The point 19 is connected to a point 20 on the reference lead 4 by a parallel circuit comprising a resistor 21 and a shutter solenoid holding coil 22. The point 19 is also connected to a circuit output terminal 23. Another switching member S3 is also available in the shutter control circuit 1 to provide a contact closure between circuit output terminals 24 and for coordinating external control circuits, such as a flash device, with the operation of the shutter control circuit 1. A shutter mechanism of the circuit 1 is actuated when an operator depresses a shutter release switch S. When the shutter release button S of the camera is depressed, switching members S1 and S2 are closed. Switching member S3 closes when the shutter of the camera is fully open. The shutter solenoid coil 22 of the camera operates on the shutter mechanism in that when the coil 22 is energized the shutter is held open but when the coil 22 becomes de-energized, the shutter is allowed to close. Such shutter mechanisms are well known in the art as shown in US Pat. No. 3,465,656 and British Pat. No. 1,265,819, for example, and a further explication of the mechanical details of the shutter mechanism 30 is therefore not presented herein.

In operation when the shutter release switch S is actuated by a photographer, power is applied between the power lead 3 and the reference lead 4 and the light sensing device 5, in conjunction with the capacitor 9, begins to integrate the light received from a scene being photographed. The transistors 7 and 11 do not conduct after the closure of the switches S1 and S2. The transistor 17 however begins to conduct when S2 is closed, and the shutter solenoid holding coil 22 is energized thereby holding the shutter of the camera open. When the shutter is fully open, S3 closes. The closure of S3 may be effectively utilized to trigger an electronic flash unit connected to the output terminals 23, 24, and 25 of the shutter control circuit 1. When a predetermined amount of light has been integrated by the light sensing device 5 and the integrating capacitor 9, the transistor 7 will become forward biased and begin to conduct current therethrough. Conduction through the transistor 7, in turn, causes the transistor 11 to turn on, thereby back biasing the'transistor l7 and terminating conduction therethrough. When the transistor 17 turns off, the shutter solenoid coil 22 is denergized and the shutter is allowed to close thereby blocking any further exposure of a light sensitive film in the camera by light received from the scene being photographed. It is noted that when the light integrating means of the camera has received'sufficient light to properly expose a light sensitive film in the camera positive going and negative going signals with respect to the reference lead 4 are generated within the shutter control circuit 1 of the camera. One positive going signal appears at the collector terminal of the transistor 11 and one negative going signal apppears at the collector terminal of the transistor 17. Either signal interalia may be designated as a terminate signal since the appearance of either signifies that the proper amount of light has been received by the camera for correct exposure of the film and-exposure of the light sensitive film may be terminated. The terminatesignal appearing at the collector of the transistor 17 is applied to the output terminal 23 and may be used to initiate the quenching operation of a connected electronic flash unit.

FIG. 2 shows the 3 wire to 2 wire adapter circuit of the present invention as it is connected in a computerflash system using the automatic shutter control circuit 1 of an auto-exposure camera 26 and an electronic flash unit 31. The three output terminals 23, 24 and 25 of the shutter control circuit 1 are connected to the input of an adapter circuit 28. The adapter circuit 28 has two output terminals 27A and 29A for providing a connection to the electronic flash unit 31.

A suitable flash unit 31 which has a pair of input or control terminals for connection to a two wire transmission line is shown schematically in FIG. 3. In pursuance of the advantages of the two wire system, theere is shown in FIGS. 4, 5, and 6, various embodiments of a three wire-to-two wire adapter or coupling circuit which will be discussed in detail hereinafter which may be used in conjunction with the electronic shutter control circuit 1 of FIG. 1, or other similar electronic shutter control circuits, to render the flash unit of FIG. 3 compatible therewith.

In FIG. 3, there is shown the flash unit 31 having two input terminals 27 and 29. The input terminal 29 is connected to a flash unit ground bus 33; the input terminal 27 is connected to a control signal bus 35. The flash unit ground bus 33 is connected to a terminal 37. A high voltage bus 39 of the flash unit 31 is connected to a terminal 41. A storage capacitor 43 is connected between the terminals 37 and 41. The terminals 37 and 41 are provided for connection to the usual capacitor charging means which is not shown in FIG. 3. Such capacitor charging means are well known in the art, and it is sufficient to say that the capacitor 43 is normally maintained in a charged state by the aforementioned capacitor charging means whereby a relatively high voltage is maintained across the capacitor 43. A flash or light producing tube 45 is shown with its anode con nected to the high voltage bus 39 and its cathode connected to the ground bus 33. A light triggering terminal 47 of the flash tube 45 is coupled through a transformer T1 to one terminal of a capacitor 49. The other terminal of the capacitor 49 is connected to the anode terminal of a silicon controlled rectifier (SCR) 51. The common terminal of the transformer T1 is connected to the bus 33. A light terminating or quench tube 53 is shown connected between the high voltage bus 39 and the ground bus 33. A quench tube triggering terminal 55 is connected through a transformer T2 to one terminal of a capacitor 57. The other terminal of the capacitor 57 is connected to the anode terminal of a second SCR 59. The common terminal of the transformer T2 is connected to the control signal bus 35. A capacitor 61 connects the high voltage bus 39 with the control signal bus 35. The control signal bus 35 is connected to the anode terminal of a Zener diode 63. The cathode terminal of the zener diode 63 is connected to a common point between the base terminal of an NPN transistor 65 and the cathode terminal of a diode 67. The anode terminal of the diode 67 is connected to the ground bus 33. The collector terminal of the transistor 65 is connected through a resistor 69 to the anode terminal of the SCR 51. The high voltage bus 39 is connected to the anode terminal of the SCR 51 through a resistor 71. The gate terminal of the SCR 51 is connected to the collector terminal of the transistor 65, and, the cathode terminal of the SCR 51 is connected to the ground bus 33. The emitter terminal of the transistor 65 is also connected to the ground bus 33. The control signal bus 35 is connected to the emitter terminal of an NPN transistor 73. The base terminal of the transistor 73 is connected through a capacitor 75 to the ground bus 33. The base terminal of the transistor 73 is also connected through a resistor 77 to the high voltage bus39. The collector terminal of the transistor 73 is connected through two resistors 79 and 81 to the high voltage bus 39. The common point between the two resistors79 and 81 is connected to the anode terminal of the SCR 59. The gate terminal of the SCR 59 is connected to the collector terminal of the transistor 73. The cathode terminal of the SCR 59 is connected to the controlsignal bus 35.

In operation, the capacitor 49 of the flash unit 31 is charged from the high voltage bus 39 through the resistor 71. The capacitor 57 of the flash unit-31 is similarly charged from the high voltage bus 39through.the resistor 81. The transistor 73 is so biasedthat. it is normally conducting, in a steady state condition. The transistor 65 is similarly so biased that it is normally conducting.

With the transistor 73 conducting, the gate terminalof the SCR 59 is effectively clampedto its cathode terminal and the SCR 59 is therefore nonconductive. Similarly, with the transistor 65 conducting, the gate terminal of the SCR 51 is effectively clampedto its cathode terminal thereby precluding conduction therethrough. When an actuation of a switching means, for example the shutter release switch S and shutter mechanism 30 of an associated camera 26, effects a contact closure between the terminals 27 and 29 of the flash unit 31, the potential of the control signal bus 35 will decrease with respect to the potential ground bus 33, since a lower resistance path between the contro'lsignal bus and the ground bus is provided by the contact closure than would otherwise be available through the Zener Diode 63 and the base emitter path of the transistor65. The reduced potential on the control signal bus 35'with respect to the ground bus 33, willcause the transistor 65 to turn off. With the transistor 65 nonconducting, a

.current will flow through the resistor 69 and into the gate terminal of the SCR 51, thereby rendering. it conductive. With the SCR 51 conducting, the relatively low resistance path thereby presented, rapidly discharges the capacitor 49, whereby to trigger the flash tube 45. As the flash tube 45 begins to conduct, the voltage on the high voltage bus 39 is suddenly reduced as the charge on the capacitor 43'is dumped through the flash tube 45. That sudden voltage decreasev appearing at the high voltage bus 39 is coupled through the capacitor 61 to the control signal bus 35. Thecoupling action of the capacitor 61 causes the voltage on the control signal bus 35 to suddenly decrease to a negative value with respect to that of the ground bus 33; and therefore, the potential at the terminal 27will go negative with respect to the potential atthe. terminal 29. That change in potential is designated as the Return signal for reasons hereinafter discussed. At this point in the operation of the flash unit 31, the flash tube 45 is heavily conducting thereby giving off light for the illumination of a scene being photographed. The next action of the flash unit 31 occurs when a remote light sensing unit, which senses light received thereby from the scene being photographed, determines that sufficient light has been received to properly expose the light sensitive filmin the camera. At that time, another effective contact closure, is provided by the associated camera. That contact closure is effective to again reduce the potential difference between the control signal bus 35 and the ground bus 33 of the flash unit 31. That potential difference decrease is coupled through the capacitor to the base terminal of the transistor 73 thereby causing the transistor 73 to cease conduction. With the transistor 73 nonconducting, a current will flow into the gate terminal of the SCR 59 thereby rendering it conductive. When the SCR 59 becomes conductive, a lower resistance discharge path is presented across the capacitor 57 of the flash unit 31 which causes the capacitor 57 to dump its charge. That action induces a triggering signal to appear at the quench tube triggering terminal 55 thereby initiating conduction in the quench tube 53. The dumping of the charge on the capacitor 57 produces a ringing action through the circuit comprising the capacitor 57, the SCR 59, and the transformer T2. That ringing action is effective to turn off the SCR 59 after the quench tube triggering signal has been provided. After being triggered, the quench tube 53 conducts much more heavily than the flash tube 45 and provides an effective short circuit across the capacitor 43. The residual charge on the capacitor 43 of the flash unit 31 will then rapidly dissipate to a point where the voltage on the high voltage bus 39 is insufficient to support ionization in either the quench tube 53 or the flashtube 45 at which time both tubes will cease conduction. The charging circuit connected to the terminals 41 and 37 of the light producing means or flash unit 3l.will then begin to recharge the capacitor 43. The voltage appearing at the high voltage bus 39 will build up to a value sufficient to restore the bias ing voltage required to turn on the transistors 65 and 73 and the flash unit 31 of FIG. 3 will be returned to its steady state condition to await the initiation of another cycle. It should be noted that the potential at the terminal 27 of the flash unit 31 is initially of a greater magnitude than the potential at the terminal 29. When an effective contact closure from an external circuit is applied thereacross, the flash unit 31 becomes operative thereby providing light to illuminate a scene to be photographed. At that time, a Return signal representative of the fact that the flash unit 31 is operative appears at the input terminals 27 and 29 in the form of a polarity reversal, i.e. the potential at the terminal 27 will go negative with respectto the potential at the terminal 29 when the flash tube 45 begins to conduct. Thereafter, a second contact closure, provided by an external circuit and representative of the fact that sufficient light has been received from a scene being photographed to properly expose a light sensitive film in an associated camera, is applied across the input terminals 27 and 29 of the flash unit 31. That second effective contact closure, which may be referred to as a quench control signal, is operable to terminate conduction in the flash tube 45 thereby terminating its light producing function. In FIG. 4, a three wire-to-two wire adapter circuit is shown for interconnecting the automatic electronic shutter control circuit of FIG. 1 with the electronic Flash unit of FIG. 3. A capacitor 81 connects an input terminal 23A of the adapter 38 to a control terminal of a Programmable Unijunction Transistor (PUT) 83. Another input terminal 25A is connected to one output terminal 29A by a lead 85. The anode terminal of the PUT 83 is connected to the lead 85; and its cathode terminal is connected to another output terminal 27A. The control terminal of the PUT 83 is connected to the lead 85 through a resistor 87. A diode 89 has its anode terminal connected to the output terminal 27A and its cathode terminal connected to another input terminal 24A The shutter control circuit of FIG. 1 is connected to the adapter circuit of FIG. 4 by connecting terminals 23 and 23A, 24 and I 24A, and 25 and 25A, respectively. The adapter circuit is connected to the electronic flash unit 31 by connecting terminals 27A and 27, and 29A and 29, respectively. When the switch S of FIG. 1 is actuated, and after the shutter of the camera 1 is fully open, the switch S3 closes, thereby providing an effective contact closure between the output terminals 27A and 29A of the adapter circuit 28. That contact closure, as hereinbefore explained, when transmitted to the flash unit 31, will initiate conduction in the flash tube 45 thereby providing light for the illumination of a scene being photographed. Thereafter, when the potential at the terminal 27 of the flash 31 decreases with respect to the potential at the terminal 29, the diode 89 becomes reversed biased thereby decoupling the initial contact closure, provided by the switch S3, from the flash unit 31. Subsequently, when sufflcient light has been received by the light responsive means of FIG. 1, the potential at the collector terminal of the transistor 17 will decrease as hereinbefore explained in connection with FIG. 1. That potential decrease is coupled through the capacitor 81 to the control terminal of the PUT 83, thereby rendering the PUT 83 conductive. With the PUT 83 conducting, an effective contact closure is again provided across the terminals 27A and 29A. That second contact closure causes the potential at the terminal 27A to increase toward the potential at point 29A. That increase in potential acts as a quench control signal since its application to the terminals 27 and 29 of the flash unit 31 is effective to quench the light given off by the flash unit 31 as hereinbefore explained. I

The Return signal, i.e. the decrease in the potential appearing at the terminal 27A, resulting from the initiation of the conduction in the flash tube 45, acts to decouple the switch 93 and also enable the PUT 83 to become conductive upon a subsequent application of the negative going signal which appears at the collector terminal of the transistor 17 when proper exposure has been accomplished. The coupling or adapter circuit, including the capacitor 81, the resistor 87, the PUT 83 and the diode89 is effective to couple an electronic shutter control circuit to an electronic flash unit thereby providing a computer flash system using only a two wire connection therebetween. The adapterrequires only a contact closure, indicative of a shutter switch actuation, and a negative going signal, indicative of a detection of a sufficient amount of light received from a scene being photographed, to properly expose a light sensitive film in the camera. Since the coupling circuit can only transmit the quench control signal to the flash unit after it has received the Return signal, the coupling or adapter circuit is insensitive to noise signals which might appear at the control electrode of the PUT 83 before the receipt of the Return signal. Therefore, the possibility of a false quenching of the Flash tube is significantly reduced.

FIG. 5 is identical to FIG. 4 except that the PUT 83 is replaced with an SCR 97 and the capacitor 81 is connected to the base terminal of the transistor 17 instead of the collector terminal thereof. The operation of the circuit of FIG. 5 is similar to that of FIG. 4 as far as the signals appearing at the output terminals 27A and 29A of the adapter are concerned. However, the circuit of FIG. 5 is provided for connection to an electronic shutter control circuit in which a positive going signal is available as representative of a detection of a predetermined amount of light by a light sensing means. Such a positive going signal in the present example appears at the base terminal of the transistor 17. That positive going signal is coupled through the capacitor 81 to the gate terminal of the SCR 97 to provide the second contact closure as herinbefore defined in connection with the operation of the flash unit 31.

The circuit of FIG. 6 illustrates a different method of coupling the electronic shutter control circuit with the flash unit 31. In FIGS. 4 and 5, capacitive coupling was used; and in FIG. 6, inductive coupling is used. Inductive or transformer coupling provides the additional advantage of complete isolation. FIG. 5 is identical to FIG. 4 except that the signal generated by the electronic shutter control circuit is coupled to the adapter circuit through the winding 22. A winding 99 in the adapter circuit 28" has a common flux path with the shutter solenoid holding winding 22. The winding 99 is connected between the cathode and gate terminals of the SCR 97. A diode 101 and a capacitor 103 are also connected individually in parallel between the cathode terminal and the gate terminals of the SCR 97. In operation, when the signal at the collector terminal of the transistor 17 decreases in response to a detection of a predetermined amount of light by the light responsive means 5, the transistor 17 becomes nonconductive. At that time, the flux built up in the coil 22 begins to collapse which in turn generates a voltage in the winding 99 which is applied between the gate and cathode terminals of the SCR 97 thereby rendering the SCR 97 conductive. The conduction through the SCR 97 provides the second contact closure for the flash unit 31 as hereinbefore explained.

Thus there has been provided in accordance with the present inventionan adapter circuit for coupling an automatic exposure control camera circuit to an electronic flash unit, using only a two wire connection therebetween, and which significantly attenuates the possibility of a false quench.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The combination comprising:

controllable electronic flash unit; and

light sensitive assembly for use in association with a camera havinga shutter mechanism, said light sensitive assembly comprising:

first and second output terminals for connection to said controllable electronic flash unit;

means responsive to an actuation of theshutter mechanism of the camera for effectively short circuiting said first and second output terminals whereby to initiate an operation of the electronic flash unit;

means responsive to the actuation of said flash unit to effectively open circuit said first and second output terminals;

light sensitive means responsive to light received from a scene to be photographed to produce an electrical signal representative of the intensity of said light received;

integrating means responsive to said electrical signal to produce an integral signal representative of the integral of the light received;

means responsive to the actuation of the shutter mechanism to enable operation of said light sensitive means and said integrating means;

means responsive to an attainment of a predetermined magnitude of said integral signal for generating a terminate signal; and

means responsive to said terminate signal to again effectively short circuit said first and second output terminals whereby to initiate a termination of the operation of said electronic flash unit.

2. A light sensitive assembly for use in associated with a camera having a shutter mechanism, said light sensitive assembly comprising:

first and second output terminals for connection to a controllable electronic flash unit; means responsive to an actuation of the shutter mechanism of the camera for effectively short circuiting said first and second output terminals whereby to initiate actuation of the electronic flash unit; means responsive to the actuation of the flash unit to effectively open circuit said first and second output terminals;

light sensitive means responsive to light received from a scene to be photographed to produce an electrical signal representative of the intensity of the light received;

integrating means responsive to said electrical signal to produce an integral signal representative of the integral of the light received;

means responsive to the actuation of the shutter mechanism to enable operation of said light sensitive means and said integrating means;

means responsive to an attainment of a predetermined magnitude of said integral signal for generating a terminate signal, and means responsive to said terminate signal to again effectively short circuit said first and second output terminals whereby to initiate the termination of the operation of the electronic flash unit.

3. An adapter for interfacing a controllable electronic flash unit with a camera having an electronically controlled shutter assembly whereinthe electronically controlled shutter assembly includes light sensitive means responsive to light received from a scene to be photographed to produce an electrical signal representative of the intensity of the light received, integrating means responsive to said electrical signal to produce an integral signal representative of the integral of the light received, a shutter mechanism, means responsive to an actuation of the shutter mechanism to enable an operation of the light sensitive means and the integrating means, and means responsive to an attainment of a predetermined magnitude by said integral signal for generating a terminate signal, said adapter comprising;

first and second output terminals for connection to the electronic flash unit;

means responsive to the actuation of the shutter mechanism for effectively short circuiting said first and second output terminals whereby to initiate an operation of said electronic flash unit;

means responsive to the actuation of the flash unit to effectively open circuit said first and second output terminals;

means responsive to said terminate signal to again effectively short circuit said first and second output terminals whereby to initiate a termination of the operation of the electronic flash unit.

4. The adapter as set forth in claim 3 wherein all the power for said adapter is applied through first and second output terminals.

5. The adapter as set forth in claim 3 wherein said adapter includes:

first, second and third input terminals arranged for connection to said camera, said third input terminal being connected to said second output terminal;

a programmable unijunction transistor (PUT) having anode, cathode and gate terminals, said PUT anode and cathode terminals being connected across said second and first output terminals, respectively;

a coupling means connecting said first input terminal with said PUT gate terminal;

diode means having anode and cathode terminals thereof connected between said first output terminal and said second input terminal; and

impedance means connected between said PUT gate terminal and said third input terminal.

6. The adapter as set forth in claim 3 wherein said adapter includes:

first, second and third input terminates arranged for connection to said camera, said third input terminal being connected to said second output terminal;

' a silicon controlled rectifier (SCR) having anode, cathode, and gate terminals, said SCR anode and cathode terminals being connected across said second and first output terminals, respectively;

a coupling means connecting said first input terminal with said SCR gate terminal;

diode means having anode and cathode terminals thereof connected between said first output terminal and said second input terminal; and

impedance means connected between said SCR gate terminal and said third input terminal.

7. The adapter as set forth in claim 3 wherein said adapter further includes means responsive to the actuation of the flash unit to enable said last mentioned means to effectively short circuit said first and second output signals in response to said terminate signal.

' UNITED STATES. PATENT OFFICE} I CERTIFICATE OF CORRECTION Patent'No, D d December 4,

Inventor(5) Dennis L]- wflwerding 'It is certified that error appears in the abbve identified patent and that said Letters Patent are hereby corrected as shown below:

Ih Claim 7, line 5, 'for ""signals" read ---term1'naIs--.

Signed and sealed this 17th day ef December 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. I c. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC scan-poo FORM PO-IOSO (10-69) I U.S. GOVERNMENT PRINTING OFFICE ll! 0-36-53l,

UNITED STATES- PATENT OFFICE CERTIFICATE OF CORRECTION Pat en 'No, 3,776,112 I Dated December 4, 1973 v Dennis J. W1 Iwevding v 'It is certified that error appears in the abcve -identified patent and that said Letters Patent are hereby corrected as shown below:

In C'laim 7, line 5, for "signals" re'ad -term1naIs-.

Signed/3nd sealed this" 17th day 10f December 1974.

( EAL) Attest:

McCOY M. GIBSON JR. Attesting Officer c. MARSHALL DANN- Commissioner of Patents FORM PC4050 I v UscoMM-Dc 60876-P69 E I U. S. GOVERNME NT FRIN'HNG OFFICE 2 "9 O"l3" 

1. The combination comprising: controllable electronic flash unit; and light sensitive assembly for use in association with a camera having a shutter mechanism, said light sensitive assembly comprising: first and second output terminals for connection to said controllable electronic flash unit; means responsive to an actuation of the shutter mechanism of the camera for effectively short circuiting said first and second output terminals whereby to initiate an operation of the electronic flash unit; means responsive to the actuation of said flash unit to effectively open circuit said first and second output terminals; light sensitive means responsive to light received from a scene to be photographed to produce an electrical signal representative of the intensity of said light received; integrating means responsive to said electrical signal to produce an integral signal representative of the integral of the light received; means responsive to the actuation of the shutter mechanism to enable operation of said light sensitive means and said integrating means; means responsive to an attainment of a predetermined magnitude of said integral signal for generating a terminate signal; and means responsive to said terminate signal to again effectively short circuit said first and second output terminals whereby to initiate a termination of the operation of said electronic flash unit.
 2. A light sensitive assembly for use in associated with a camera having a shutter mechanism, said light sensitive assembly comprising: first and second output terminals for connection to a controllable electronic flash unit; means responsive to an actuation of the shutter mechanism of the camera for effectively short circuiting said first and second output terminals whereby to initiate actuation of the electronic flash unit; means responsive to the actuation of the flash unit to effectively open circuit said first and second output terminals; light sensitive means responsive to light received from a scene to be photographed to produce an electrical signal representative of the intensity of the light received; integrating means responsive to said electrical signal to produce an integral signal representative of the integral of the light received; means responsive to the actuation of the shutter mechanism to enable operation of said light sensitive means and said integrating means; means responsive to an attainment of a predetermined magnitude of said integral signal for generating a terminate signal, and means responsive to said terminate signal to again effectively short circuit said first and second output terminals whereby to initiate the termination of the operation of the electronic flash unit.
 3. An adapter for interfacing a controllable electronic flash unit with a camera having an electronically controlled shutter assembly wherein the electronically controlled shutter assembly includes light sensitive means responsive to light received from a scene to be photographed to produce an electrical signal representative of the intensity of the light received, integrating means responsive to said electrical signal to produce an integral signal representative of the integral of the light received, a shutter mechanism, means responsive to an actuation of the shutter mechanism to enable an operation of the light sensitive means and the integrating means, and means responsive to an attainment of a predetermined magnitude by said integral signal for generating a terminate signal, said adapter comprising; first and second output terminals for connection to the electronic flash unit; means responsive to the actuation of the shutter mechanism for effectively short circuiting said first and second output terminals whereby to initiate an operation of said electronic flash unit; means responsive to the actuation of the flash unit to effectively open circuit said first and second output terminals; means responsive to said terminate signal to again effectively short circuit said first and second output terminals whereby to initiate a termination of the operation of the electronic flash unit.
 4. The adapter as set forth in claim 3 wherein all the power for said adapter is applied through first and second output terminals.
 5. The adapter as set forth in claim 3 wherein said adapter includes: first, second and third input terminals arranged for connection to said camera, said third input terminal being connected to said second output terminal; a programmable unijunction transistor (PUT) having anode, cathode and gate terminals, said PUT anode and cathode terminals being connected across said second and first output terminals, respectively; a coupling means connecting said first input terminal with said PUT gate terminal; diode means having anode and cathode terminals thereof connected between said first output terminal and said second input terminal; and impedance means connected between said PUT gate terminal and said third input terminal.
 6. The adapter as set forth in claim 3 wherein said adapter includes: first, second and third input terminates arranged for connection to said camera, said third input terminal being connected to said second output terminal; a silicon controlled rectifier (SCR) having anode, cathode, and gate terminals, said SCR anode and cathode terminals being connected across said second and first output terminals, respectively; a coupling means connecting said first input terminal with said SCR gate terminal; diode means having anode and cathode terminals thereof connected between said first output terminal and said second input terminal; and impedance means connected between said SCR gate terminal and said third input terminal.
 7. The adapter as set forth in claim 3 wherein said adapter further includes means responsive to the actuation of the flash unit to enable said last mentioned means to effectively short circuit said first and second output signals in response to said terminate signal. 